McKee, who directs the Yale Tobacco Treatment Clinic, said quitting strategies have been geared to male biology. Most target the nicotine receptors in the brain, the ones that send feel-good signals when the person smokes. But McKee says women are more likely to smoke to cope with stress, not to get those feel-good signals.

She's now testing drugs that help women to relax, hoping that these will also help them quit. Dozens of women smokers regularly visit her New Haven lab to test her hypothesis.

"Our preliminary results are encouraging," McKee said, adding that it will take a few more years to reach a conclusion.